1. Field of the Invention
The present invention relates to a liquid crystal display device, and a liquid crystal display provided with such a liquid crystal display device.
2. Description of the Related Art
Recently, liquid crystal displays which display images by driving liquid crystal display devices have been widely utilized for picture display units such as televisions and a monitors, and information terminals such as digital cameras and mobile phones, because of their low-profile, light-weight, and small power-consumption characteristics. In such liquid crystal displays, as liquid crystal display system of the liquid crystal display devices, there are known twisted nematic (TN) mode using nematic liquid crystal, vertical alignment (VA) mode, in plane switching (IPS) mode, and fringe field switching (FFS) mode (refer to Japanese Unexamined Patent Publication No. Hei-06-160878). In addition, there are known display modes using ferroelectric liquid crystal, antiferroelectric liquid crystal, or the like.
FIG. 5 illustrates a cross-sectional configuration of a liquid crystal display device of typical VA mode. In this liquid crystal display device, a liquid crystal layer 500 including a liquid crystal molecule 500A is sealed between a drive substrate 200 and a facing substrate 300. In respective facing planes of the drive substrate 200 and the facing substrate 300, there are provided an electrode 202 and an electrode 302, liner projections 410 which do not face each other, alignment films 400 covering over the electrodes 202 and 302, and the liner projections 410. In VA mode, a liquid crystal molecule 500A is oriented substantially perpendicular to planes of the alignment films 400, with no voltage applied. Therefore, the liquid crystal molecule 500A is slightly inclined to surfaces of the drive substrate 200 and the facing substrate 300, in a region in the vicinity of the liner projection 410 (that is, tilt is provided). On the other hand, the liquid crystal molecule 500A is oriented substantially perpendicular to the surfaces of the drive substrate 200 and the facing substrate 300, in a region except the region in the vicinity of the liner projection 410. When the voltage is applied to the liquid crystal layer 500 in this state, the inclination of the liquid crystal molecules 500A located in the vicinity of the liner projection 410 is propagated in sequence to other liquid crystal molecules 500A, and those liquid crystal molecules 500A respond so as to take a posture falling substantially horizontal to the surfaces of the drive substrate 200 and the facing substrates 300. Accordingly, an entering light is modulated. This is because the liquid crystal molecule in VA mode shows a negative dielectric anisotropy; in other words, has a property that the dielectric constant in the long-axis direction of the molecule is smaller than that in the short-axis direction of the molecule.
However, there occurs a difference between the speed, in response to the applied voltage, of falling of the liquid crystal molecule 500A which is oriented perpendicular to the surfaces of the drive substrate 200 and the facing substrate 300, and the speed of falling of the liquid crystal molecule 500A which is located in the vicinity of the linear projection 410, and an issue arises that the response speed of the liquid crystal molecules 500A as a whole with the voltage applied is delayed. Especially, in gradation change from black to intermediate colors, the change amount of the voltage to be applied is small, and this further promotes delay of the response speed. Also, the response speed can be accelerated by shortening the distance between the respective linear projections 410; however, because the upper surface of the linear projections 410 does not contribute to the transmissivity of liquid crystal display device, there arises an issue that, as the ratio of the projections in the liquid crystal display device is increased, the transmissivity is reduced and the display characteristics are degraded.
Thus, Japanese Unexamined Patent Publication No. 2002-357830 proposes the technique in the above VA mode to slightly incline the liquid crystal molecule from the substrate normal and maintain the inclination by using high-polymer materials so that the tilt is provided. Specifically, a liquid crystal layer in which a monomer having light polymerization is added for composition is sealed between substrates, and then is exposed in the state that the tilt is provided to the liquid crystal molecule by applying the voltage so that the monomer is polymerized so as to form the liquid crystal display device forming. In this way, a direction of falling of the liquid crystal molecule can be set in advance in the state with no voltage applied, and this improves the response speed.